1. Field of the Invention
The present invention relates to a vehicle power control device mounted in an electrical vehicle or the like, particularly to a vehicle power control device in which the ordinary electric generation function can be switched to the auxiliary electric generation function when abnormality occurs.
2. Description of the Related Art
In an electric powered vehicle such as an electric car or a hybrid car, a motor generator (hereinafter referred to as “M/G”) is equipped in place of a conventional diode rectification type electric generator for the high value-added purpose such as driving/braking of a vehicle, starting of a motor and an internal combustion engine mounted on the vehicle, or electric generation for charging a battery, and a power converter (popularly named as inverter) for M/G driving control. A microcomputer, a dedicated LSI or the like is used as means for generating a power element driving signal of the power converter, and many control signal patterns have been proposed in order to simplify the system construction and enhance the energy efficiency.
For example, Patent Document 1 (JP-A-2001-271729 (paragraph 0030 and FIG. 1)) has proposed the following technique. That is, in a case where the shaft of a brushless motor (permanent magnet motor) is linked to the output shaft of an engine and the brushless motor is operated as a starter for the engine, a chopper circuit is set to a non-operation state or operated as a voltage increasing chopper to thereby drive the brushless motor through an inverter circuit. In addition, in a case where the brushless motor is operated as an electric generator, when an electric generation voltage of the brushless motor is higher the voltage of a battery, the inverter circuit is set to a non-operation state and the chopper circuit is made to operate as a high-voltage chopper, thereby charging the battery, and when the electric generation voltage of the brushless motor is lower than the voltage of the battery, the transistor of the chopper circuit is set to an ON-state, and the transistor at the negative side of the inverter circuit is turned on and off, thereby making the inverter circuit operate as a voltage increasing chopper, thereby charging the battery.
Furthermore, Patent Document 2 (JP-A-6-178441 (paragraph 0008 and FIG. 1)) has proposed the following technique. That is, initial excitation at the start time of the internal combustion engine is carried out by an electronic device as a charging control device containing a microcomputer, and the output voltage of an alternating electric generator is controlled to a preset charging voltage of a battery. When the terminal voltage detecting terminal of the battery is slipped, the normal charging voltage control can be performed by using the voltage value of an operating power source of the electronic device, and thus neither a second rectifier nor a dedicated electric circuit is needed. Furthermore, when the charging voltage exhibits an abnormal value with respect to a target charging voltage, a field coil current supplying circuit is enforcedly interrupted to prevent overcharge, and also a charge lamp is turned on and off to warn the driver.
According to these techniques, the voltage of the battery and the charging/discharging amount are controlled on the basis of the signal pattern of the driving signal generating means of the power element such as the inverter circuit or the like which constitutes the power converter. Accordingly, when the power element driving signal generating means of the power converter does not normally function due to breakdown or the like, it is difficult to perform regeneration or electrical generation. Furthermore, even when only the gate signal of the power element is stopped to set the power element to a diode rectifying mode so that the field coil current can be continued to be controllable, the whole electric generation is stopped when the function of the microcomputer is stopped. Furthermore, when the charging to the battery is suddenly stopped, the time which is needed for the driver to move his/her vehicle to a safe place is restricted to a very short time. Conversely, when the current supply of the field coil cannot be stopped, over-excitation occurs, so that a critical defect such as overcharge of the battery or the like as a power source system for a vehicle may be caused.